In the UK, September is a transitional month in terms of lawn care. The weather is still relatively mild, but the days are getting shorter, and there will likely be more rainfall. Here are some key lawn care tasks to focus on in September:

1. Mowing: Continue to mow your lawn regularly, but gradually raise the cutting height of your mower as the month progresses. This helps prepare the grass for the cooler months ahead. Aim to keep the grass around 2.5 to 3 inches in height.
2. Aeration: If your lawn suffers from compacted soil or poor drainage, consider aerating it in September. Aerating helps improve air circulation and water penetration into the soil. You can use aeration tools or hire a professional lawn care service.
3. Weed Control: Keep an eye out for weeds and address them promptly. Hand weeding or spot treating with an appropriate weed killer can help prevent them from spreading and taking over the lawn.
4. Fertilisation: September is a good time for a late summer/early autumn fertilisation. Choose a balanced, slow-release fertiliser that is suitable for your grass type. This will help strengthen the grass before winter.
5. Overseeding: If your lawn has thin or bare patches, consider overseeding in September. September is ideal for seeding as the ground temperature is still warm but there is less chance of heat stress during germination. Choose a grass seed mix that is suitable for the UK climate and your specific grass type. Ensure good seed-to-soil contact and keep the area consistently moist until the new grass establishes itself.
6. Dethatching: If your lawn has a thatch problem (a layer of dead grass and debris), consider dethatching it in early September. Dethatching tools or machines can help remove this layer and improve the lawn's health. A spring rake will work just as well but may require a bit more hard work!
7. Pest and Disease Control: Early autumn is prime time for any pests or diseases to take hold, as conditions are perfect; warm and moist! Keep an eye out for signs of lawn pests or diseases. Address any issues promptly with appropriate treatments or remedies.
8. Lawn Equipment Maintenance: This is a good time to give your lawn care equipment some TLC to keep them in good working order. Sharpen mower blades, clean filters, and perform any necessary maintenance to keep them running smoothly. You will thank yourself for this when you bring them out again in spring!
9. Leaf Management: As autumn progresses, leaves will start falling from trees. Regularly remove fallen leaves from your lawn, as they can smother the grass and create ideal conditions for disease.

Remember that the specific tasks you need to undertake may vary depending on your lawn type and local climate conditions. You may not need to do every task on this list but its good to understand what they are and identify if they are required.